Telephone system



(No Model.)

J. J. GARTY.

TELEPHONE SYSTEM.

UNITED STATES PATENT OFFICE.

JOHN J. OARTY, OF NEl/V YORK, N. Y., ASSIGNOR TO THE AMERICAN BELLlELEPI-IONE COMPANY, OF BOSTON, MASSACHUSETTS.

TELEPHONE SYSTEM.

SPECIFICATION forming part of Letters Patent No. 425,863, dated April15, 1890.

Application filed November 13, 1889- Serial No. 330,126. (No model.)

To all whom it may concern:

Be it known that I, JOHN J. CARTY, residing at New York, in the countyof New York and Stateof New York, have invented certain Improvements inCentralization of Transmitter-Batteries, of which the following is aspecification.

This invention relates to telephone -exchange work, and provides a planwhereby a battery located at the central station is enabled to energizethe transmitters at a plurality of sub-stations without the necessity ofemploying a special battery-wire extending from the said central stationto all of the substations which are to be supplied.

Althoughbattery-transmitters are of course capable of being operatedwith their working electrodes included together with a battery directlyinthe main telephone-circuit, it has been found usually more economicaland efficient,except where the said main circuits were very short or ofparticularly low resistance, to include the transmitter-electrodes ateach sub-station with one or two cells of battery in the primary orcoarse-wire helix of an induction-coil, the secondaryhelix whereof wasincluded in the main-line circuit. The variations of current produced bythe operation of the transmitter in the primary helix have thus beeninductively transferred .to the secondary helix and mainline, over whichthey have passed to the distant receiving telephone. Heretofore a planhas been devised by Charles E. Scribner, for which Letters Patent No.243,165, and dated June 21, 1881, have been issued, whereby a batterylocated at the central station may be caused to supply without mutualinterference the transmitters of a number of sub-stations, thusdispensing with the separate battery at each subscribers station whichhad been required, and thereby effecting a considerable economy in time,la bor, and expense. This plan, briefly stated, is carried out byplacing the current-varying part of the transmitter in one of the armsof a Wheatstone bridge organized at the subscribers station, and byconnecting the primary helices of an induction-coil also 10- A cated atsaid sub-station and associated with said transmitter in the cross-wireof said bridge system. The battery-current is conveyed to thetransmitters at the various substations of a group by means of an extrawire extended between them and the central station. In any case,however, an extra supply-wire is not a desirable adjunct, and becomesvery burdensome when the actual telephone-circuit is itself a metalliccircuit, by reason both of its additional cost, which is not materiallyless than that of the local batteries which it displaces, and also byreason of the inconvenience attending the leading into the sub-stationof so many conductors.

The object of this invention is wherever metallic circuits are employedto dispense with the local transmitter-batteries at the subscribersstations by supplying the substation transmitters with current from acommon battery located at the central station, and to do this withoutadding in place thereof an extra battery-wire. this by utilizing the twowires of each metallic circuit considered and connected as a singleconductor of increased cross-section,as the conducting-circuit of theenergizing battery-current. By using the same two wires as the two sidesof a metallic circuit for a conversation-circuit, and by the use of asuitable induction-coil (preferably of the class known in the art asrepeating-coils) in each 's'ub station metallic circuit at the centralstation, the said repeating induction-coil being connected by a wireleading from the center of one of its helices (that connected with themain-line wires) to earth through the ener- 'gizing-battery. I retainthe use of the bridge arrangement at the sub-stations.

The drawing, which illustrates and formsa part of this specification, isa diagram ofthe electrical connections necessary to carry out myinvention in the operation of metallic circuits centering at a telephonecentral station.

In the drawing, 0 denotes a central telephone-station, and S asubscribers station. At the former R is an ordinaryswitoh-board, of anypreferred construction, provided with the regular operators connecting,calling, and supervising outfit of devices in a manner well understoodin the art. At the sub-station S is shown the subscribers apparatusviz.,his call sending and receiving appliances, the transmitting andreceiving telephones, and

I am enabled to do the primary current-controlling devices, hereinafterto be more fully described.

M is the metallic circuit subscribers line, composed of the two wires 1and 2. Tracing line-wire 1,it passes on, entering the subscribersstation to the automatic telephone-switch s, which makes contact withpoint I) when the the receiver is at rest and in place and withcontact-point 0 when the telephone-receiver is removed from the switch,as shown. From I) a branch wire 5 passes, connecting throughcall'sending generator D and call-bell d with line-wire 2 at m. This isthe normal or calling circuit of the metallic-circuit telephoneline.From the point 0 a wire 6 extends, continuing the circuit through onehelix eof the receiving-telephone T and one helix 9 of the inductorium Nand by wire 8 to a point I. From the point Z the circuit extends by wire11 through the other helix h of the inductorium N, and then by wire 10through the second coil f of the receiving-telephoneT and to theline-wire 2. p

The receiving-telephone and inductoriumhelices are differentiallywound-that is to say, 6 is wound inopposition to f, and g is wound inopposition to h-so that they tend to determine magnetic neutrality intheir respective cores so far as the primary effect of the battery B isconcerned, and it is prefera ble to have coils e and f of equalresistance and coils g and h likewise of equal resistance.

The helices g and h of the induction-coil N have a common primary helix1', which is included .by means of wires 12 and 13 in the cross orbridge wire of the \Vheatstone bridge system W. One of thejunction-points 16 of the second system is grounded at E, and the otherjunction-point 17 is connected by wire 9 with the point Z of thesubscribers metallic circuit. Care should be taken to have the two sides1 and 2 of the metallic talking-circuit balanced with respect toresistance and capacity.

The operative parts of the transmitterviz.,

its current-varying electrodes, which are con-' trolled bythe diaphragmare included in one of the arms of the bridge, and suitable resistances,as indicated at w, as, and x are in cluded in the remaining arms of thebridge,

as well understood. In this respect I adopt the construction ofScribners Patent No. 243,165, hereinbefore cited.

At the central station is an ordinary repeating induction-coil I, suchas the standard repeating-coil, which has its two wires substantiallyalike in size" and number of con volutions. are joined, respectively, tothe central-station ends of the two sides 1 and 2 of the metallicsubscribers circuit. A wire V is attached to the center of this helixand from thence leads to one pole of the supply-battery B, the otherpole of which by wire 2; is connected to earth at E The other helix ofthis repeating-coil is connected at one of its ends with a groundwire Eand at the other with a wire 3 lead- The two ends of one of thesehelices,

ing to the line spring-jack J, and thence through the said jack by wire4to the annunciator-drop r and ground at E.

The operators apparatus being of any ordinary and well'known character,need not here be described. I

Instead of terminating both ends of the central station repeating-coilhelix to earth, as shown, if desired, two spring-jacks may be provided,and the two ends of said helix run to their respective springs. In thatcase the two fixed contacts of the two jacks would be united by a wirehaving the annunciator 0' in its circuit. The operation of signalingover this circuit will readily be understood. Incoming calls transmittedby means of the generator D traverse the metallic circuit and actinginductively through the coil I actuate the annunciator awhile outgoingcalls are sent, as usual, by means of the operators calling appliances,which are brought into connection with the line by means of the plug P,which may be inserted in the spring-jacks J, the signals thus sent alsoacting inductively upon the line through the coil I.

The operation of the subs'cribers transmitter is as follows: Theactuating-battery B is already described located at the central station,and thus is always under the control of the said station. When thetelephone at the sub-station is on the switch, the circuit of saidbattery is open. When the receiving-telephone is removed from theswitch, but before tlie transmitter is being used, the current from thebattery B divides and flows part-1y I through the wire 1 and partlythrough the wire 2 to the sub-station S, as indicated by the arrows 0and 0'. These currents,aftr passing through thereceiving andtransmitting helices e and fand g and h, unite once niore at the point Z and passon through a single conductor 9 through the bridge NV and to earth.Unless the bridge organizationis perfectly balanced some portion ofthecurrent necessarily passes by the way of the bridge-wire, whichincludes the primary helix 4' even when the transmitter is at rest.When, however, the transmitter is being operated, its resistance iscaused to vary continually, and a.corre spending variation of currentoccurs in the primary coil 1; of the inductorium, which induces thevarying currents in the secondary coils, which currents circulate in thelinewires 1 and 2 and are at any given moment in the two wires of adirection indicated by the arrows q and q'that is, they are of opposingdirection in the two wires. It will be noted that q tends to oppose 0',and consequently at the moment we are considering the resultant currentin 2 is of smaller volume; but it may also be notedthatthe current in 1is correspondingly increased by the coincident and co-operative presenceof the two eurrentsof like direction, represented by the arrows 0 and q,

total current developed by the secondary helices and flowing in themetallic circuit is and as a consequence the not affected by nor does itaffect the primary current, and since the repeating-coil 1, concerned inthe transmission of the voice-currents, is operated solely by the saidcurrents, developed by the substation inductorium secondary, andcirculating in the metallic circuit composed of the two wires 1 and 2,it is evident that no detrimental effect can occur from the apparentconflict of the original and induced currents. On the contrary, theuseful eifect may be regarded as being proportionate to the differencebetween the electrical state of the two sides of the metallic circuitwhen at rest and that when the transmitter is being operated.

M and M are similar subscribers circuits extending to sub-stations S andS the substation transmitters of which are energized by the same batteryB, from which the wires V and V branch, each to its own metalliccircuit. The several metallic circuits each have their ownrepeating-coils I and I and the branches V and V connect with theirmetallic circuits at the center of the mainline helices of such coils.The other helices of the repeating-coils are, as in the case of thefirst circuit, adapted for connection with a spring-jack J and calldevice I.

Having now fully described my invention, I claim- 1. In a system fortelephonic communication, the combination, with a telephone-transmitterat one station and an energizing-battery therefor at another station,ofa doublewire circuit extending between the two stations and includingsaid transmitter in a metallic circuit, both of said wires being inconnection with the same pole of said battery, thereby constitutingjointly a single conductor of relatively high conductivity for thebattery-currents, substantially as described.

2. In a'telephone system, the combination of aseries or group ofmetallic telephone-circuits extending each from a central station to aseparate sub-station, a telephone-transmitter at each sub-stationincluded in its own metallic circuit, and an energizing-battery for thesaid transmitters common to the group and connected with all of the saidmetallic circuits, the two wires of each-of the said circuits beingconnected with one pole of said battery, thereby constituting jointly apractically single conductor for the battery-current in multiple are orparallel circuit with the other similarly-constituted single con-'ductors of the group, substantially as described.

' 3. The combination, substantially as hereinbefore described, of ametallic circuit extending between a centraland a sub station, with aninduction-coil at the central station having one of its helices includedin a local circuit, with the switch-board connecting and signalingdevices, and having its other helix included in the said metalliccircuit, and a battery included in a branch circuit extending from apoint at the center of the metallic circuit helix to earth, togetherwith a transmitting and receiving telephone and induction-coil for theformer, and a Vheatstone bridge, all at the sub-station, thereceiver-helix and the secondary helix being each formed of twocoils,one in each wire of the metallic line-circuit and differentiallywound or connected, the Wheatstone bridge being included in a branchcircuit extension from a neutral point on the said metallic circuit toearth, the primary helix of the induction-coil being in the cross-wireof said bridge and the Variable resistance of the transmitter beingconnected in one of the arms of said bridge, whereby the two wires ofthe metallic circuit in connection with the terminal earth branches mayjointly constitute the transmitter-battery circuit, while they mayseverally form the two sides of the conversation-current circuit.

4. The combination of a metallic circuit, an earth branch therefor ateach terminal station thereof, a WVheatstone bridge at one of the saidstations included in the said earth branch,'a telephone-transmitter andits in? duction-coil, the secondary helix of said coil being composed oftwo equal parts, one part in each wire of the said metallic circuit (thesaid circuit being assumed to terminate'at the junction-point of itsearth branch) and the primary helix of said coil being included in thecross-wire of said bridge, and a battery included in the earth branch atthe other station, substantially as described, and for the purpose setforth.

5. A metallic telephone-circuit, extending between a central and a substation, an earth branch united to the said metallic circuit at eachterminal station at such central points as to balance the two sides ofsaid circuit, a

telephone transmitter and receiver at the sub-station and an inductioncoil for the former, the receix'enhelix and the main-line helix of saidinduction-coil being halved between the two sidesv of the circuit, asdefined by the point of connection of the earth branch,

and a \Vheatstone bridge included in said earth branch, the primaryhelix of the induction-coil being in the cross-wire, and the IICtransmitter being in one of the arms of said bridge, in combination witha battery in the central-station earth branch, a repeating-coilconnected as described and having one of its helices in the metalliccircuit and the other in a local switch-board circuit, including aspring-jack and a call-annunciator, substan tially as hereinbefore setforth.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 9th day of No vember, 1889.

JOHN J. CARTY.

WVitnesses:

HERBERT LAWS WEBB, O. A. BELL.

